1. Field of the Invention
The present invention relates to a data storing apparatus including magnetic memory cells and semiconductor devices, which can be used as a main memory, by utilizing a hysteresis property of a ferromagnetic body, and reading and writing data in accordance with electromagnetic induction, with an element such as a transistor for controlling current therethrough in both directions.
2. Description of the Related Art
A main memory for computers is conventionally comprised of:
(1) SRAM (Static Random Access Memory), PA1 (2) DRAM (Dynamic Random Access Memory), PA1 (3) EEPROM (Electrically Erasable Programmable Read Only Memory), PA1 (4) flush memory, PA1 (5) ferroelectric memory, or PA1 (6) core memory.
The SRAM is a semiconductor memory which utilizes an on/off action of a flip-flop circuit. Generally, by using a bistable condition of a pair of transistors when memorizing, it is possible to perform a non-destructive readout. Thus, the SRAM is capable of storing data rapidly and statically. However, as current always flows through the SRAM, and it is necessary to have a large number of elements in the SRAM, it is disadvantageous to consume a large amount of electric power and occupy a large area of the memory. Moreover, as the SRAM has a volatile property, it is disadvantageous to erase data in the memory when a power supply thereof is turn-off.
The DRAM is a semiconductor memory which utilizes a charge of one or more capacitors. It can generally be composed of a small number of MOS transistors which are main components. Further, the entire area of the memory can be made small by using one or more capacitors which have a three dimensional form as one or more memory elements. In the DRAM, as the discharges stored as the information have been lost as time goes, it is necessary to refresh the DRAM at a constant interval to maintaining data in the DRAM. Further, as the destructive readout is carried out in the DRAM, a data rewriting is needed after the memory is read. Moreover, as the DRAM also have the volatile property, it is disadvantageous to erase the memory when the power supply is turned-off.
The EEPROM and the flush memory are semiconductor memories which are reloadable read only memories. They are classified as non-volatile memories which do not erase data even if a power supply thereof is turned-off. In case where the EEPROM or the flush memory is used, the difference between the reading time thereof and the writing time thereof is large, so that the reading time is asymmetrical to the writing time. Also, it is unfavorable to have less number of writable times than the SRAM and the DRAM.
The ferroelectric memory is a memory which has been developed recently, and it can be constructed as a high-speed and non-volatile memory or a memory which is able to be used in non-destructive readout mode. In term of the ferroelectric memory, the selection of material which is composed of the thin film of the ferroelectric body and the technique of the formation thereof are not fully established, and the property of matter about the thin film which guarantees the reliability thereof is not obvious. Also, it is disadvantageous to have less number of writable times than the SRAM and the DRAM. Therefore, it cannot be used instead of the SRAM or the DRAM as the main memory in these days.
The core memory is a typical memory which utilizes magnetization of the core. The use of such a memory has been quite popular in the past. It also has a non-volatile property. In case of the core memory, it can carry out the non-destructive readout in rapid and non-volatile manner. However, it does not suit the mass production because the assembling thereof needs the manual working, so that the manufacture thereof get hard as the mass storing is desired, and it have not used rapidly as the semiconductor memories such as the SRAM, the DRAM, or the like have been developed. An operating system at the present time when the core memory has been quite popular, does not fully put to practice use the core memory having the non-volatile property.
On the other hand, a memory element having one or more magneto-resistance elements has been recently proposed. Such a memory utilizes a magneto-resistance effect or giant magneto-resistance effect, and develops from a technique in a magnetic head of a hard disc. In the memory element having one or more magneto-resistance elements which utilizes the magneto-resistance effect or giant magneto-resistance effect, the magneto-resistance element is in way of development and the magneto-resistance element is mainly utilized in a magnetic head of a hard disc, so that the research and development of the magnetic head are mainly carried out and it has not put into practice as the main memory for computers yet.
It is highly desirable that a memory can be operated at high-speed, has a large capacity and non-volatile property. However, none of the above-mentioned conventional memory devices satisfies the above mentioned conditions at the same time.